Re: [化學] 中興化學問題

[water0bearer (霖)]

※ 引述《sparkle0829 (sparkle)》之銘言：
: ......
: 98.3. Consider the following chemical reaction: 2A + 2B → C  Overall reaction
:       Reaction mechanism: Step1. A+B→D
:                           Step2. D+B→M
:                           Step3. A+M→C
:       Which one of the following rate laws is consistent with this mechanism?
:       (A) Rate = k[A]^2 [B]   (B) Rate = k[D][B]  (C) Rate = k[A][B]
:       (D) Rate = k[A] [B]^2   (E) The information is not sufficient
: →請問這樣列是錯哪?
:   Step3: K2 = [M]/[D][B] ; K1 = [D]/[A][B] ; [M]=K2[D][B]=K2K1[A][B]^2
:          Rate[C] = K3[A][M] =  K1K2K3 [A]^2 [B]^2

我認為是E，不知道哪一部是速率決定步驟~

: 98.6. Gasoline was injected into the cylinder and was ignited. A piston moved
:       outwardly of the cylinder while exposition took place inside the motor
:       engine. Which of the following statements is not accurate ?
:       (A) It is an example of converting chemical energy to mechanical work.
:       (B) The motor engine had done work to the surrounding.
:       (C) The temperature dropped down after the piston moved out.
:       (D) All the energy released from the burning of gasoline was converted
:           to the work done to the surrounding.
:       (E) It was an irreversible process.
: →是否選E,不可逆表自發,但其被ignite才氣體膨脹？

E是對的，答案我認為應該是D。
現實生活中幾乎所有的反應在熱力學夏都是不可逆的(不能回到原本的狀態)。
引擎燃燒爆炸有一大部分的能量變成熱能散失到surrounding，
並沒有全部用來做功!

: 98.10. Which of the following statements is wrong about thermodynamics ?
:        (A) The entropy of any substance(element or compound)in its equilibrium
:            state approaches zero at the absolute zero of temperature.
:        (B) The absolute value of the Gibbs free energy of a substance can't
:            be determined.
:        (C) The Gibbs free energy is zero during phase transitions of a pure
:            substance.
:        (D) The absolute value of the entropy of a substance can't be
:            determined.
:        (E) A spontaneous process is always an irreversible process.

我猜是C，相變化自由能會變吧!

: 95.29. What is W in Boltzmann's formula, S=k x InW
:        (A) a fraction indicating the probability of obtaining a result
:        (B) a random number
:        (C) the number of ways of obtaining the state
:        (D) the work times Avogadro's number
: →請問這定律是？

應該是A，
普化課本有這個方程式，我記得~
你可以查看看書本後面的字母索引!

: 94.18. If the temperature of the reaction is decreased, what is the effect on
:        the equilibrium constant and ΔG ?
:        N2(g) + 3H2(g) → 2NH3(g),ΔH+ = -92.4 kJ/mol
:        (A) K increases, ΔG increases
:        (B) K decreases, ΔG decreases
:        (C) K increases, ΔG decreases
:        (D) K decreases, ΔG increases
:        (E) Temperature does not affect equilibrium or ΔG
: →請問G是？1. K↑,G= -RTlnK (兩個變因 T↓K↑)
:            2. K↑,G=  H-TS, T減少到負值，此時G↑    故選A？

K會上升你知道，
G的部分我認為這個反應在低溫會趨向自發，
所以溫度越低ΔG應該愈來愈小~

: 94.非選擇題1. Please describe how to set up the physical structure of atom using the
:               experimental findings.
: 題目有點多T_T   今天被教授劣退  有請各位大大幫忙了!感恩!!

抱歉~目前手邊沒有計算紙與筆，
也沒有普化課本，
先回答你這樣，
沒回答的另請高手幫忙~

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推 veryblack:98.3=你的想法是對的 不知道哪一步是決定步驟(slow)
→ veryblack:98.10=純物質相變化時自由能變化為零喔   是亂度會變
推 veryblack:所以是D 亂度可以直接求出值
→ veryblack:這年我有考過= = 不過熱化學一年沒碰了大概只記得這些
→ sparkle0829:水大和v大先謝謝你們  94.18怎麼判斷低溫趨向自發?
推 sparkle0829:另外亂度 不是要計算系統與環境?不是因為不好測所以才
→ sparkle0829:改用ΔG只需檢測系統資料 因為環境不知道怎麼測?
推 veryblack:亂度質有公式可以帶
→ veryblack:G(自由能的話) 則只能求出變化量 無法得知其值是多少
→ veryblack:94.18=利用deltaG = deltaH - T x deltaS
→ veryblack:利用deltaG>0可自發<0非自發來判斷
→ veryblack:而T是絕對溫度 故其值必大於零
→ veryblack:所以就可以得知當deltaH>0時 若deltaS也大於零
推 sparkle0829:了解!
→ veryblack:更正 若deltaS小於零時 算出來deltaG必大於零 自發
→ veryblack:反之就必小於零 非自發
推 sparkle0829:這題沒給s 是否用S=H/T
推 veryblack:deltaS可以自行判斷 例如液相便氣相會變大之類的
→ veryblack:反應過程中莫耳數變少亂度也是下降
→ veryblack:因此可以得知deltaS<0
推 sparkle0829:所以ΔS<0 ΔT<0 此G應該為下降了
推 veryblack:可是這題的溫度有改變所以不是用這條公式= =
→ veryblack:不好意思我剛沒注意到
推 sparkle0829:ΔG=Δ(H-TS)=ΔH-T*ΔS-S*ΔT  我好像越來越模糊了XD
推 veryblack:還是請專家解釋好了XD
→ veryblack:這題我那時候很直接的想K變大deltaG必變更小(負更大)
→ veryblack:剛翻了一下普化還是想不出解釋方式